membranes Review Past, Present and Future of Surgical Meshes: A Review Karen Baylón 1, Perla Rodríguez-Camarillo 1, Alex Elías-Zúñiga 1, Jose Antonio Díaz-Elizondo 2, Robert Gilkerson 3 and Karen Lozano 4,* 1 Centro de Innovación en Diseño y Tecnología, Tecnológico de Monterrey, Campus Monterrey, Monterrey 64849, Mexico; [email protected] (K.B.); [email protected] (P.R.-C.); [email protected] (A.E.-Z.) 2 Escuela de Medicina, Tecnológico de Monterrey, Campus Monterrey, Monterrey 64849, Mexico; [email protected] 3 Departments of Biology and Clinical Laboratory Sciences, The University of Texas Rio Grande Valley, Edinburg, TX 78539, USA; [email protected] 4 Mechanical Engineering Department, The University of Texas Rio Grande Valley, Edinburg, TX 78539, USA * Correspondence: [email protected]; Tel.: +1-956-665-7020 Received: 15 June 2017; Accepted: 17 August 2017; Published: 22 August 2017 Abstract: Surgical meshes, in particular those used to repair hernias, have been in use since 1891. Since then, research in the area has expanded, given the vast number of post-surgery complications such as infection, fibrosis, adhesions, mesh rejection, and hernia recurrence. Researchers have focused on the analysis and implementation of a wide range of materials: meshes with different fiber size and porosity, a variety of manufacturing methods, and certainly a variety of surgical and implantation procedures. Currently, surface modification methods and development of nanofiber based systems are actively being explored as areas of opportunity to retain material strength and increase biocompatibility of available meshes. This review summarizes the history of surgical meshes and presents an overview of commercial surgical meshes, their properties, manufacturing methods, and observed biological response, as well as the requirements for an ideal surgical mesh and potential manufacturing methods. Keywords: surgical mesh; hernia repair; abdominal wall reconstruction; biocompatibility 1. Introduction A hernia is defined as a protrusion or projection (prolapse) of an organ through the wall of the cavity where it is normally contained [1]. There are many types of hernia, mostly classified according to the physical location, with the abdominal wall being the most susceptible site. Specifically, reports show that the most frequently seen hernia is the inguinal hernia (70–75% of cases), followed by femoral (6–17%) and umbilical (3–8.5%) hernias [2]. Hernias are also found in other sites such as the ventral or epigastric hernia, located between the chest cavity and the umbilicus. Hernias can be uncomfortable and are sometimes accompanied by severe pain, which worsens during bowel movements, urination, heavy lifting, or straining [3]. Occasionally, a hernia can become strangulated, which occurs when the protruding tissue swells and becomes incarcerated. Strangulation will interrupt blood supply and can lead to infection, necrosis, and potentially life-threatening conditions [4]. Hernia repair is one of the most common surgical procedures performed globally. It is estimated that there are over 20 million hernia repair procedures per year worldwide [5]. The number of procedures has been increasing and is predicted to further increase due to several risk factors such as Membranes 2017, 7, 47; doi:10.3390/membranes7030047 www.mdpi.com/journal/membranes Membranes 2017, 7, 47 2 of 23 obesity and prior abdominal surgeries [6]. Hernia repairs provide an important revenue stream for hospitals, estimated at $48 billion/year in the United States [7]. The use of hernia mesh products to surgically repair or reconstruct anatomical defects has been widely adopted: in fact, more than 80% of hernia repairs performed in United Sates use mesh products [8]. The surgical mesh firmly reinforces the weakened area and provides tension-free repair that facilitates the incorporation of fibrocollagenous tissue [9]. However, there are many types of meshes and there is a strong controversy regarding optimum performance and success of surgical procedures. Researchers have investigated metals, composites, polymers and biodegradable biomaterials in their quest to attain the ideal surgical mesh and implantation procedure [10]. The sought-after characteristics are inertness, resistance to infection, the ability to maintain adequate long-term tensile strength to prevent early recurrence, rapid incorporation into the host tissue, adequate flexibility to avoid fragmentation, non-carcinogenic response and the capability to maintain or restore the natural respiratory movements of the abdominal wall [9]. Currently, utilized surgical meshes exhibit many but not all of the desired characteristics [8]. Therefore, current research efforts focus on providing potential solutions that range from the utilization of novel materials to new designs that could ameliorate existent shortcomings [11]. The aim of this review is to illustrate the current research in surgical meshes used for hernia repair. This review provides a perspective of existent commercial surgical meshes, their properties, manufacturing procedures, and observed biological responses. Furthermore, the article seeks to establish the requirements for an ideal surgical mesh and potential manufacturing procedures. 2. History In 1890, Theodor Billroth suggested that the ideal way to repair hernias was to use a prosthetic material to close the hernia defect [12]. Many materials were used, but all failed due to infections, rejections, and recurrences [13]. Surgeons concluded that the main problem was built upon the multifilament suture material, which has been proven unsuitable in many other surgical procedures [14]. Surgeons became disenchanted with the popular cotton and silk sutures because of the frequently observed rejection syndrome and resultant endless recurring infections. The use of such sutures to secure mesh in place undoubtedly contributed to aggravate the existing bias against the surgical meshes [15]. In 1955, Dr. Francis Usher focused his attention on the materials that could solve existing problems. Nylon, Orlon, Dacron and Teflon were studied and were observed to have a variety of shortcomings such as: foreign body reaction, sepsis, rigidity, fragmentation, loss of tensile strength and encapsulation [16]. All of these precluded the acceptance of polymeric materials. After reading an article about a new polyolefin material (Marlex), which demonstrated remarkable properties, Usher started to develop a woven mesh [17]. Two years later, the marlex prostheses were implemented. These were made of large pores, which facilitated incorporation despite infections. The growth of tissue through its interstices was the main difference when compared to previous materials. After a few days of surgical incorporation, fibroblast activity was noticed to increase, more collagen was induced without giant cells, and the whole system gained strength [18]. Despite the numerous advantages of the woven and knitted polyethylene mesh, Usher continued the search for better systems. He soon found that knitted polypropylene had many more advantages: it could be autoclaved, had firm borders coupled with two-way stretching, and could be rapidly incorporated. Finally, in 1958, Usher published his surgical technique using a polypropylene mesh, and 30 years later the Lichtenstein repair (known today as “tension-free” mesh technique) was popularized for hernia repair [18]. Even when the benefits of meshes were accepted, the recollection of evidence-based cases was required to statistically quantify their advantages. In 2002, the European Union Hernia Trialists Collaboration, a group of surgical trialists who have participated in randomized trials of open mesh or laparoscopic groin hernia repair, analyzed 58 randomized controlled trials and concluded that the use of surgical meshes was superior to other techniques [19]. In particular, they noted fewer recurrences and less postoperative pain with Membranes 2017, 7, 47 3 of 23 mesh repair. These results were supported by other studies that demonstrated that hernia repair using surgical meshes reduced the risk of hernia recurrence compared to hernia reconstruction through other methods, in 2.7% vs. 8.2% in ventral hernia repair cases and by 50–75% of improvement through surgical meshes in inguinal repair [8]. Today, many surgeons agree that use of a prosthetic mesh is the preferred way to repair hernias. It should be emphasized that in the past, the success of repair was evaluated based on the strength and permanency of the mesh itself, not on the degree of scar tissue or other factors, which subsequently develop in and around the mesh [20]. The biocompatibility of the material has proven to be a strong contributor in the rejection of the prosthesis due to scar tissue developed by the immunological system. When a surgical mesh is implanted and lacks appropriate biocompatibility (either due to the material that it is made of or its structural design) the body responds by encapsulating the foreign system leading to the formation of a stiff scar which consequently results in poor tissue incorporation, causing hernia recurrence or infection of the mesh. A large percentage of meshes then have to be removed: approximately 69% of the explanted meshes are due to prosthesis infection [21]. Although the only treatment is surgery, there are new surgical procedures that ameliorate postoperative side effects such as the laparoscopic approach. Open surgery repair is performed by making an incision in the abdomen to identify